In a semiconductor device, leakage current results in faulty operation of the semiconductor device. The leakage current includes a gate induced drain leakage(GIDL) current. The GIDL current is generated in a drain region overlapped with a gate electrode.
FIG. 1 illustrates a plan view of a conventional semiconductor device. Referring to FIGS. 1 and 2, in a general semiconductor device, an isolation layer 102 is formed at a predetermined region of a semiconductor substrate 100 to define an active region 104. A gate electrode 124 crosses over the active region 104. A gate oxide layer 122 is interposed between the gate electrode 124 and the active region 104. A shallow channel diffusion layer 106 is formed in the active region 104 under the gate oxide layer 122. A source region 130 and a drain region 132 are present in the active region 104, adjacent to the channel diffusion layer 106. The source region 130 and the drain region 132 have a region ‘A’ overlapped with the gate electrode 124.
FIG. 3 illustrates a diagram indicating the ‘A’ region of FIG. 2 to illustrate a GIDL current in a semiconductor device. Referring to FIG. 3, the GIDL current is generated by a band-to-band tunneling resulting from a high electric field which is induced between the gate electrode 124 and the drain region 132. Thus, electron-hole pairs are generated, so that carriers flow out toward the semiconductor substrate 100 having a relatively lower potential than the drain region 132.
The leakage current also includes a subthreshold leakage current meaning that a current flows via the substrate under the gate electrode. As a result, a transistor is turned on at a lower voltage than an operation voltage.
FIG. 4 illustrates a cross-sectional view taken along a II–II′ line of FIG. 1 illustrating a subthreshold leakage current of a semiconductor device. Referring to FIG. 4, when a shallow trench isolation technology is applied, the gate oxide layer 122 becomes thin at the boundary B between the active region 104 and the isolation layer 102, and this may result in an inverse narrow width effect. Thus, the transistor is turned on at a lower gate voltage than the operation voltage, and thus, a subthreshold leakage current flows via the substrate under the gate electrode 124.